One of America's best-known counter-cultural comedians, Tommy Chong, is facing the prospect of a nine-month jail sentence after being convicted of selling glass pipes on the internet which can be used for smoking cannabis.

Lawyers for Chong, 65, one half of the famous Cheech and Chong comedy duo and more recently a television actor, claim the US attorney general, John Ashcroft, chose to prosecute him for the publicity value. The glass pipes, or "bongs", that Chong has been offering for sale are the same as those that have been sold for years by thousands of "head shops" all over the US and Europe, and Chong has regularly been paying taxes on their sales.

"They are really prosecuting him for who he is," his Los Angeles-based attorney, Richard Hirsh, said yesterday. "It was a very selective prosecution. Ashcroft is 100% behind it."

Mr Hirsh said that for many years the sale of bongs and pipes had been accepted and no notice had been given of an intended change in policy.

Twenty-two people have been convicted of selling pipes since Mr Ashcroft launched Operation Pipe Dreams last year. Some 650,000 people in the US are arrested each year for minor cannabis possession.

Chong, who has no previous convictions and has run his business in Gardena, California, alongside an acting career, was arrested after a sting operation in which federal agents in Pittsburgh ordered bongs over the internet, thus ensuring that the items were sent across state lines.

Judge Arthur Schwab said jail was appropriate for "a felony of conspiring to distribute drug paraphernalia", and sentenced him to nine months last week. His lawyers are deciding whether to appeal.

Chong, who was born in Canada, linked up with "Cheech" Marin in the 1970s and made a number of comedy films with a cannabis-related theme. Among them were Up In Smoke, Cheech and Chong's Nice Dreams, Still Smokin' and, in the 1990s, National Lampoon's Senior Trip. His latest film is Pot Luck.